1. Field
Example embodiments relate to light-emitting devices and methods of manufacturing the same.
2. Description of the Related Art
Semiconductor light-emitting devices (LEDs) are high efficient and environmentally friendly light sources that are widely used in various applications such as display devices, optical communications, vehicles, and/or general lighting. As white-light LED technology has developed, LED technology for general lighting has attracted much attention. A white-light LED may be made by using a blue or ultra violet (UV) LED together with a fluorescent material and/or made by combining red, green, and blue LEDs.
A blue or UV LED, which is a main element of a white-light LED, is generally made using a gallium nitride (GaN)-based compound semiconductor. GaN-based compound semiconductors have a wide band-gap and can obtain light from almost a full wavelength region ranging from visible light to UV, the wavelength depending on the composition of a nitride therein.
Luminance efficiency is an important consideration in designing an LED. The luminance efficiency depends on lattice differences between components constituting the LED and on a difference between thermal expansion coefficients. When an InGaN layer is used as a light-emitting material, an emission spectrum (e.g., color) may be altered by modifying a mole fraction of indium (In) included in the InGaN layer. As the In content is increased, the emission spectrum moves towards longer wavelengths. However, as the In content is increased, a lattice constant is increased, and a lattice mismatch increases between a thin film type InGaN layer and a substrate, lowering the luminance efficiency. As the emission spectrum moves toward a longer wavelength, the luminance efficiency is decreased.
A p-n junction may be formed in the form of a one-dimensional nano structure, such as a nanowire, a nanopillar, and/or a nanocolumn by using a GaN-based compound semiconductor and/or a zinc oxide. Research has been conducted on technology for forming a nanoscale LED. Lattice constant mismatch between a substrate and a one-dimensional nano structure and a difference in thermal expansion coefficients may have less of an impact on luminance efficiency as compared to a thin film type InGaN layer.